A sealed and thermally insulated tank for the storage of liquefied natural gas which is integrated in a load-bearing structure such as the double hull of a marine vessel designed for the transport of liquefied natural gas is disclosed in the document WO 2014 167213. The tank has a multilayer structure successively having, in the direction of the thickness from the outside to the inside of the tank, a secondary thermally insulating barrier retained on the load-bearing structure, a secondary sealing membrane bearing against the secondary thermally insulating barrier, a primary thermally insulating barrier bearing against the secondary sealing membrane and a primary sealing membrane designed to be in contact with the liquefied natural gas contained in the tank.
The secondary sealing membrane consists of a plurality of metal sheets having two perpendicular corrugations protruding toward the outside of the tank and thus permitting the secondary sealing membrane to be deformed under the action of thermal stresses generated by the fluid stored in the tank. The secondary thermally insulating barrier has a plurality of insulating panels of standard dimensions juxtaposed against the load-bearing structure and separated by interstices. Each metal sheet of the secondary sealing membrane has a length and a width substantially corresponding to those of the standard insulating panels of the secondary thermally insulating barrier and is arranged offset relative to said insulating panels such that it extends across four of the insulating panels and that the corrugations of the corrugated metal sheets are inserted inside the interstices separating said insulating panels.
In the region of a corner between two walls, the secondary thermally insulating barrier has an angled structure composed of two angled insulating panels which are respectively arranged against the load-bearing structure of both of the two walls and together form a corner of the secondary thermally insulating barrier. Each of these two angled insulating panels has on its internal face a metal connecting strip. A metal angle plate is welded to the metal connecting strip of each of the two angled insulating panels so as to provide the seal of the secondary sealing membrane. At the edge of each wall, corrugated metal sheets provide the connection of the secondary sealing membrane to the angled structure by being welded to the metal connecting strips. The dimensions of the metal sheets at the edge of the wall may be different from those of the other metal sheets, so as to be adapted to the dimensions of the angled structure.
The arrangement of the secondary thermally insulating barrier and of the aforementioned secondary sealing membrane, however, is not entirely satisfactory.
More specifically, on the one hand, such an arrangement does not permit the structural dimensional tolerances of the secondary thermally insulating barrier of each wall to be compensated, due in particular to the tolerance margins during the manufacture of the load-bearing structure. More specifically, the structural tolerances of the load-bearing structure are capable of reaching several centimeters, for example in the order of 4 cm.
Moreover, such an arrangement imposes limitations regarding the dimensions of the tanks which are able to be manufactured. More specifically, the dimension between two angled structures arranged in the region of two opposing corners of a tank wall has to correspond substantially to an integer multiple either of the width or of the length of a standard insulating panel of the secondary thermally insulating barrier.